The increasing reliance on communication networks to transmit more complex data, such as voice and video traffic, is causing a very high demand for bandwidth. To resolve this demand for bandwidth, communications networks are relying upon optical fiber to transmit this complex data. Conventional communication architectures that employ coaxial cables are slowly being replaced with communication networks that comprise only fiber optic cables. One advantage that optical fibers have over coaxial cables is that a much greater amount of information can be carried on an optical fiber.
Meanwhile, one problem that data service providers face when changing from coaxial cables to optical fibers is the expense of building their own optical network. Similar to traditional coaxial cable networks, in order for a service provider to compete with another service provider, it has been typical business practice for the service provider to build its own network relative to the network of the competing service provider.
Instead of the service providers building their own separate optical networks, some municipalities have proposed constructing optical networks for their residents in which service providers could share the newly constructed optical networks. One proposed conventional way for service providers to share a municipal optical network is by using digital signals such as internet protocol (IP) packets to support data as well as voice and video services.
For video services, transmitting video information in IP packets would require digital optical transmitters to modulate a digital optical carrier. Digital optical receivers would be needed to demodulate the digital optical carrier. And digital electrical receivers such as digital set top terminals (STTs) or boxes would be required to decipher the video services contained in the IP packets. Such set top boxes are expensive and make implementing an all digital optical network very cost prohibitive for both the municipality and the service providers.
To eliminate the need of set top boxes to support digital video services, service providers could modulate analog optical carriers of different wavelengths with analog electrical Radio Frequency (RF) signals. Once the analog optical carriers are converted to the electrical domain at the subscriber location, a television (TV) set could easily process the video information from the electrical video signals without the need of a set top box. However, at least one problem exists when multiple service providers attempt to share an optical network using analog optical signals propagating at different wavelengths: Stimulated Raman Scattering (SRS).
SRS can cause mutual interference between two broadcast signals occupying the same RF channel on different optical wavelengths on the same optical waveguide. SRS is typically made worse by longer optical waveguides and, effectively, by larger splitting ratios. SRS can create crosstalk between the two signals on different wavelengths. For analog TV applications, crosstalk manifests itself as a ghost image of the other signal in the best case, and as a beat (moving lines in the picture) in the worst and most common case.
Accordingly, there is a need in the art for a system and method for communicating optical signals between a data service provider and a subscriber that can eliminate the effects of SRS when multiple data service providers are sharing a single optical network using optical carriers of different wavelengths. Another need exists in the art for supporting analog optical carriers of different wavelengths for large distances in an optical network in which numerous optical carriers can be split several times. Another further need exists in the art for a method and system that can support both analog and digital optical carriers in order to provide video as well as data services such as internet connections and telephone services.